NASA's next great space telescope has arrived

The long-awaited James Webb Space Telescope is set to launch this week on a journey to reconstruct the history of the universe.

Why it matters: The telescope, billed as the Hubble Space Telescope's successor, is designed to peer into the atmospheres of distant alien planets and see some of the first galaxies that formed after the Big Bang.

Driving the news: The JWST is expected to launch on Christmas Eve at 7:20am ET from Kourou, French Guiana.

• You can watch the launch live via NASA TV starting at 6am ET here.

The big questions: For decades, scientists have tried to piece together the early history of the universe, and the JWST is the first observatory that may give them a real shot at answering long-standing questions. They include:

• How do stars evolve within massive clouds of dust?
• What are the atmospheres of distant planets made of — and how different are they from Earth?
• How did the first galaxies assemble after the Big Bang?

"This telescope will not just rewrite our history of the early universe, but write it," Caitlin Casey, a University of Texas at Austin scientist who plans to use the JWST for her research, told Axios. "There are so many unknowns and blanks that we haven't yet filled in."

• For the project Casey is leading, the JWST will stare deeply at a patch of sky about three times the size of the Moon in our night sky, hopefully capturing a view of some of the universe's earliest galaxies.
• Casey and her colleagues will use that data to try to piece together a cohesive picture of what the universe looked like not long after it formed.
• The JWST will peer out into the universe primarily in infrared light making it more able to cut through dust and capture the faint light emitted by distant, early galaxies more efficiently than the Hubble.

The backstory: The $10 billion JWST has faced a number of technical setbacks, delays and a ballooning budget during its decades-long development.

• The telescope was recommended by a committee in 1996.
• Construction began in 2004, but the project quickly ballooned, at one point being called the "telescope that ate astronomy."
• Getting this telescope to space will allow other big projects in line behind it — like the Nancy Grace Roman Space Telescope — to eventually launch.

Between the lines: The JWST delays, however, have allowed scientists and engineers to include science goals that weren't possible when the telescope began development.

• When the observatory's development began, scientists hadn't yet found many planets around stars other than the Sun. Today, they know there are thousands of them.

• "It's fully possible that we might be able to find bio-signatures of life in the atmospheres of other planets," Steven Finkelstein, a scientist using the JWST to learn more about galaxies, told Axios.

Yes, but: All of this science hinges on the telescope actually working the way it's meant to, and a safe launch is only the beginning.

• Once the JWST gets to space, it will spend about a month in transit to a point about 1 million miles from Earth. (Unlike the Hubble Space Telescope, this observatory won't be close enough to our planet for an astronaut servicing mission if something were to go wrong.)
• During that transit, the telescope's large sunshield, its instruments and mirrors will all deploy over the course of weeks.
• NASA calls it "the most complex sequence of deployments ever attempted in a single space mission," noting there are more than 300 single points of failure items that could go wrong.

The bottom line: "No one has ever before unfolded a telescope in space," JWST scientist Jane Rigby told Axios. "What we're doing is necessary — astronomy simply cannot advance in some key areas until we build bigger telescopes, and that means telescopes that have to unfold."

• "I'm confident because we have the best engineering team in the world, we've practiced this on the ground over and over, we've tested all the hardware, and now it's time."